Exploring the effect of the presence of familiar people in interpersonal space

When we communicate with other people face-to-face, we do so by maintaining a certain physical distance from each other. This space surrounding our body while interacting is called the interpersonal space (IPS) and maintaining adequate IPS is crucial for better communication.

Many studies have investigated the psychological and physiological changes that occur based on the presence of another person in the IPS during face-to-face interactions. These studies are based on the avoidance behavior that we experience when a stranger invades our IPS, which manifests in the form of increased heart rate and discomfort. However, having a social relation with a person, such as with a friend or a spouse, can influence this behavior. Moreover, most studies have only examined IPS in front of or behind a person, using tasks such as a stopping task, wherein a stranger approaches or retreats from the IPS. They have not determined the shape of IPS by considering different relative positions around a person.

Addressing this gap, a team of Japanese researchers investigated the effect of social relationships on the physiological and psychological responses to the presence of another person in the IPS.

What the researchers say: “Considering a real-life situation in which acquaintances or friends are standing next to us, the threat level might be relatively low compared to when strangers are standing next to us. Given the evidence, that smaller IPSs may be formed with family and friends, psychological and physiological responses can differ. In this study, we uncovered these differences,” the lead author explained.  The team’s findings were published in the journal Scientific Reports.

The researchers used electrocardiogram (ECG) data to measure the changes in subjective discomfort, heart rate, and heart rate variability (HRV), which indicates parasympathetic activity or the “rest and digest” nervous response, of a person due to the presence of another person at various relative positions in the IPS. They measured these changes during two experiments. In the first, participants were paired with their friends standing still, where a person stood 30 cm away from the other, with both hands behind their back, within the IPS for a minute.

“There were eight relative positions in all: F-see, L-see, R-see, and B-see, as well as F-seen, L-seen, R-seen, and baseline,” the researchers said. “In the first case, participants stood face-to-face with their friend and looked at the center of their eyes. In the next three cases, they looked at their friend’s left profile, right profile, and back, respectively, with their eyes fixed on the head. In the other experiment, the participants stood with their eyes fixed on the fixation point 30 cm in front of them while being seen at their left profiles, right profiles, and backs by their friend in F-seen, L-seen, and R-seen conditions, respectively. Lastly, in the baseline condition, both people were standing back-to-back, unable to see each other. In the second task, a cylindrical object with height same as that of the person was placed at different positions in the IPS.”

The experiments revealed that the greatest discomfort, the greatest decrease in heart rate, and the greatest increase in HRV occurred in the F-see condition. The researchers attributed the decrease in heart rate and increase in parasympathetic activity to the presence of familiar people, as previous studies have shown that the presence of a friend or romantic partner activates parasympathetic activity. Moreover, they found that heart rate only decreased in relative positions F-see and R-see. Additionally, no changes were observed during the task with the object.

“These findings are inconsistent with previous studies which report that sympathetic activity, or the ‘flight or fight’ response, is activated when a stranger invades our personal space,” the lead author explained. “Our study suggests that social relationships between two people influence our physiological responses during social interactions. Our findings could help in the development of a society that makes life easier for a diverse range of people, by introducing appropriate communication methods that vary according to changes in responses to the presence of others.”

So, what? This is a fascinating study, especially in the light of recent studies of present-day hunter-gatherer people.

What makes us comfortable enough with other people to allow them to be physically closer to us—in our “interpersonal space?” The obvious answer is the depth of the relationship. My own observations of H-G bands and people in many other societies leads me to a different conclusion. The bonding that can reduce an individual’s interpersonal space depends primarily on the number of things including ideas, assumptions, beliefs, customs, rituals and physical characteristics that are shared with the other person.

We are comfortable with friends because we have developed commonality with them. It’s the commonality that allows the more intimate spacial tolerances. I believe that, for example, two ardent DT supporters would be happy with being in each other’s interpersonal space, even if they’d never met before.

The less the interpersonal space matters, the closer the bond, and the more likely they are to collaborate and defend each other—and their common beliefs, rituals and assumptions.